/*
* Copyright (c) 1997, 2011, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*
*/
#include "precompiled.hpp"
#include "classfile/javaClasses.hpp"
#include "classfile/symbolTable.hpp"
#include "classfile/systemDictionary.hpp"
#include "gc_interface/collectedHeap.inline.hpp"
#include "memory/filemap.hpp"
#include "memory/gcLocker.inline.hpp"
#include "oops/oop.inline.hpp"
#include "oops/oop.inline2.hpp"
#include "runtime/mutexLocker.hpp"
#include "utilities/hashtable.inline.hpp"
// --------------------------------------------------------------------------
SymbolTable* SymbolTable::_the_table = NULL;
Symbol* SymbolTable::allocate_symbol(const u1* name, int len, TRAPS) {
// Don't allow symbols to be created which cannot fit in a Symbol*.
if (len > Symbol::max_length()) {
THROW_MSG_0(vmSymbols::java_lang_InternalError(),
"name is too long to represent");
}
Symbol* sym = new (len) Symbol(name, len);
assert(sym != NULL, "new should call vm_exit_out_of_memory if C_HEAP is exhausted");
return sym;
}
bool SymbolTable::allocate_symbols(int names_count, const u1** names,
int* lengths, Symbol** syms, TRAPS) {
for (int i = 0; i< names_count; i++) {
if (lengths[i] > Symbol::max_length()) {
THROW_MSG_0(vmSymbols::java_lang_InternalError(),
"name is too long to represent");
}
}
for (int i = 0; i< names_count; i++) {
int len = lengths[i];
syms[i] = new (len) Symbol(names[i], len);
assert(syms[i] != NULL, "new should call vm_exit_out_of_memory if "
"C_HEAP is exhausted");
}
return true;
}
// Call function for all symbols in the symbol table.
void SymbolTable::symbols_do(SymbolClosure *cl) {
const int n = the_table()->table_size();
for (int i = 0; i < n; i++) {
for (HashtableEntry<Symbol*>* p = the_table()->bucket(i);
p != NULL;
p = p->next()) {
cl->do_symbol(p->literal_addr());
}
}
}
int SymbolTable::symbols_removed = 0;
int SymbolTable::symbols_counted = 0;
// Remove unreferenced symbols from the symbol table
// This is done late during GC. This doesn't use the hash table unlink because
// it assumes that the literals are oops.
void SymbolTable::unlink() {
int removed = 0;
int total = 0;
size_t memory_total = 0;
for (int i = 0; i < the_table()->table_size(); ++i) {
for (HashtableEntry<Symbol*>** p = the_table()->bucket_addr(i); *p != NULL; ) {
HashtableEntry<Symbol*>* entry = *p;
if (entry->is_shared()) {
break;
}
Symbol* s = entry->literal();
memory_total += s->object_size();
total++;
assert(s != NULL, "just checking");
// If reference count is zero, remove.
if (s->refcount() == 0) {
delete s;
removed++;
*p = entry->next();
the_table()->free_entry(entry);
} else {
p = entry->next_addr();
}
}
}
symbols_removed += removed;
symbols_counted += total;
// Exclude printing for normal PrintGCDetails because people parse
// this output.
if (PrintGCDetails && Verbose && WizardMode) {
gclog_or_tty->print(" [Symbols=%d size=" SIZE_FORMAT "K] ", total,
(memory_total*HeapWordSize)/1024);
}
}
// Lookup a symbol in a bucket.
Symbol* SymbolTable::lookup(int index, const char* name,
int len, unsigned int hash) {
for (HashtableEntry<Symbol*>* e = bucket(index); e != NULL; e = e->next()) {
if (e->hash() == hash) {
Symbol* sym = e->literal();
if (sym->equals(name, len)) {
// something is referencing this symbol now.
sym->increment_refcount();
return sym;
}
}
}
return NULL;
}
// We take care not to be blocking while holding the
// SymbolTable_lock. Otherwise, the system might deadlock, since the
// symboltable is used during compilation (VM_thread) The lock free
// synchronization is simplified by the fact that we do not delete
// entries in the symbol table during normal execution (only during
// safepoints).
Symbol* SymbolTable::lookup(const char* name, int len, TRAPS) {
unsigned int hashValue = hash_symbol(name, len);
int index = the_table()->hash_to_index(hashValue);
Symbol* s = the_table()->lookup(index, name, len, hashValue);
// Found
if (s != NULL) return s;
// Otherwise, add to symbol to table
return the_table()->basic_add(index, (u1*)name, len, hashValue, CHECK_NULL);
}
Symbol* SymbolTable::lookup(const Symbol* sym, int begin, int end, TRAPS) {
char* buffer;
int index, len;
unsigned int hashValue;
char* name;
{
debug_only(No_Safepoint_Verifier nsv;)
name = (char*)sym->base() + begin;
len = end - begin;
hashValue = hash_symbol(name, len);
index = the_table()->hash_to_index(hashValue);
Symbol* s = the_table()->lookup(index, name, len, hashValue);
// Found
if (s != NULL) return s;
}
// Otherwise, add to symbol to table. Copy to a C string first.
char stack_buf[128];
ResourceMark rm(THREAD);
if (len <= 128) {
buffer = stack_buf;
} else {
buffer = NEW_RESOURCE_ARRAY_IN_THREAD(THREAD, char, len);
}
for (int i=0; i<len; i++) {
buffer[i] = name[i];
}
// Make sure there is no safepoint in the code above since name can't move.
// We can't include the code in No_Safepoint_Verifier because of the
// ResourceMark.
return the_table()->basic_add(index, (u1*)buffer, len, hashValue, CHECK_NULL);
}
Symbol* SymbolTable::lookup_only(const char* name, int len,
unsigned int& hash) {
hash = hash_symbol(name, len);
int index = the_table()->hash_to_index(hash);
Symbol* s = the_table()->lookup(index, name, len, hash);
return s;
}
// Suggestion: Push unicode-based lookup all the way into the hashing
// and probing logic, so there is no need for convert_to_utf8 until
// an actual new Symbol* is created.
Symbol* SymbolTable::lookup_unicode(const jchar* name, int utf16_length, TRAPS) {
int utf8_length = UNICODE::utf8_length((jchar*) name, utf16_length);
char stack_buf[128];
if (utf8_length < (int) sizeof(stack_buf)) {
char* chars = stack_buf;
UNICODE::convert_to_utf8(name, utf16_length, chars);
return lookup(chars, utf8_length, THREAD);
} else {
ResourceMark rm(THREAD);
char* chars = NEW_RESOURCE_ARRAY(char, utf8_length + 1);;
UNICODE::convert_to_utf8(name, utf16_length, chars);
return lookup(chars, utf8_length, THREAD);
}
}
Symbol* SymbolTable::lookup_only_unicode(const jchar* name, int utf16_length,
unsigned int& hash) {
int utf8_length = UNICODE::utf8_length((jchar*) name, utf16_length);
char stack_buf[128];
if (utf8_length < (int) sizeof(stack_buf)) {
char* chars = stack_buf;
UNICODE::convert_to_utf8(name, utf16_length, chars);
return lookup_only(chars, utf8_length, hash);
} else {
ResourceMark rm;
char* chars = NEW_RESOURCE_ARRAY(char, utf8_length + 1);;
UNICODE::convert_to_utf8(name, utf16_length, chars);
return lookup_only(chars, utf8_length, hash);
}
}
void SymbolTable::add(constantPoolHandle cp, int names_count,
const char** names, int* lengths, int* cp_indices,
unsigned int* hashValues, TRAPS) {
SymbolTable* table = the_table();
bool added = table->basic_add(cp, names_count, names, lengths,
cp_indices, hashValues, CHECK);
if (!added) {
// do it the hard way
for (int i=0; i<names_count; i++) {
int index = table->hash_to_index(hashValues[i]);
Symbol* sym = table->basic_add(index, (u1*)names[i], lengths[i],
hashValues[i], CHECK);
cp->symbol_at_put(cp_indices[i], sym);
}
}
}
Symbol* SymbolTable::basic_add(int index, u1 *name, int len,
unsigned int hashValue, TRAPS) {
assert(!Universe::heap()->is_in_reserved(name) || GC_locker::is_active(),
"proposed name of symbol must be stable");
// We assume that lookup() has been called already, that it failed,
// and symbol was not found. We create the symbol here.
Symbol* sym = allocate_symbol(name, len, CHECK_NULL);
// Allocation must be done before grabbing the SymbolTable_lock lock
MutexLocker ml(SymbolTable_lock, THREAD);
assert(sym->equals((char*)name, len), "symbol must be properly initialized");
// Since look-up was done lock-free, we need to check if another
// thread beat us in the race to insert the symbol.
Symbol* test = lookup(index, (char*)name, len, hashValue);
if (test != NULL) {
// A race occurred and another thread introduced the symbol, this one
// will be dropped and collected.
delete sym;
assert(test->refcount() != 0, "lookup should have incremented the count");
return test;
}
HashtableEntry<Symbol*>* entry = new_entry(hashValue, sym);
sym->increment_refcount();
add_entry(index, entry);
return sym;
}
bool SymbolTable::basic_add(constantPoolHandle cp, int names_count,
const char** names, int* lengths,
int* cp_indices, unsigned int* hashValues,
TRAPS) {
Symbol* syms[symbol_alloc_batch_size];
bool allocated = allocate_symbols(names_count, (const u1**)names, lengths,
syms, CHECK_false);
if (!allocated) {
return false;
}
// Allocation must be done before grabbing the SymbolTable_lock lock
MutexLocker ml(SymbolTable_lock, THREAD);
for (int i=0; i<names_count; i++) {
assert(syms[i]->equals(names[i], lengths[i]), "symbol must be properly initialized");
// Since look-up was done lock-free, we need to check if another
// thread beat us in the race to insert the symbol.
int index = hash_to_index(hashValues[i]);
Symbol* test = lookup(index, names[i], lengths[i], hashValues[i]);
if (test != NULL) {
// A race occurred and another thread introduced the symbol, this one
// will be dropped and collected. Use test instead.
cp->symbol_at_put(cp_indices[i], test);
assert(test->refcount() != 0, "lookup should have incremented the count");
delete syms[i];
} else {
Symbol* sym = syms[i];
HashtableEntry<Symbol*>* entry = new_entry(hashValues[i], sym);
sym->increment_refcount(); // increment refcount in external hashtable
add_entry(index, entry);
cp->symbol_at_put(cp_indices[i], sym);
}
}
return true;
}
void SymbolTable::verify() {
for (int i = 0; i < the_table()->table_size(); ++i) {
HashtableEntry<Symbol*>* p = the_table()->bucket(i);
for ( ; p != NULL; p = p->next()) {
Symbol* s = (Symbol*)(p->literal());
guarantee(s != NULL, "symbol is NULL");
unsigned int h = hash_symbol((char*)s->bytes(), s->utf8_length());
guarantee(p->hash() == h, "broken hash in symbol table entry");
guarantee(the_table()->hash_to_index(h) == i,
"wrong index in symbol table");
}
}
}
//---------------------------------------------------------------------------
// Non-product code
#ifndef PRODUCT
void SymbolTable::print_histogram() {
MutexLocker ml(SymbolTable_lock);
const int results_length = 100;
int results[results_length];
int i,j;
// initialize results to zero
for (j = 0; j < results_length; j++) {
results[j] = 0;
}
int total = 0;
int max_symbols = 0;
int out_of_range = 0;
int memory_total = 0;
int count = 0;
for (i = 0; i < the_table()->table_size(); i++) {
HashtableEntry<Symbol*>* p = the_table()->bucket(i);
for ( ; p != NULL; p = p->next()) {
memory_total += p->literal()->object_size();
count++;
int counter = p->literal()->utf8_length();
total += counter;
if (counter < results_length) {
results[counter]++;
} else {
out_of_range++;
}
max_symbols = MAX2(max_symbols, counter);
}
}
tty->print_cr("Symbol Table:");
tty->print_cr("Total number of symbols %5d", count);
tty->print_cr("Total size in memory %5dK",
(memory_total*HeapWordSize)/1024);
tty->print_cr("Total counted %5d", symbols_counted);
tty->print_cr("Total removed %5d", symbols_removed);
if (symbols_counted > 0) {
tty->print_cr("Percent removed %3.2f",
((float)symbols_removed/(float)symbols_counted)* 100);
}
tty->print_cr("Reference counts %5d", Symbol::_total_count);
tty->print_cr("Histogram of symbol length:");
tty->print_cr("%8s %5d", "Total ", total);
tty->print_cr("%8s %5d", "Maximum", max_symbols);
tty->print_cr("%8s %3.2f", "Average",
((float) total / (float) the_table()->table_size()));
tty->print_cr("%s", "Histogram:");
tty->print_cr(" %s %29s", "Length", "Number chains that length");
for (i = 0; i < results_length; i++) {
if (results[i] > 0) {
tty->print_cr("%6d %10d", i, results[i]);
}
}
if (Verbose) {
int line_length = 70;
tty->print_cr("%s %30s", " Length", "Number chains that length");
for (i = 0; i < results_length; i++) {
if (results[i] > 0) {
tty->print("%4d", i);
for (j = 0; (j < results[i]) && (j < line_length); j++) {
tty->print("%1s", "*");
}
if (j == line_length) {
tty->print("%1s", "+");
}
tty->cr();
}
}
}
tty->print_cr(" %s %d: %d\n", "Number chains longer than",
results_length, out_of_range);
}
void SymbolTable::print() {
for (int i = 0; i < the_table()->table_size(); ++i) {
HashtableEntry<Symbol*>** p = the_table()->bucket_addr(i);
HashtableEntry<Symbol*>* entry = the_table()->bucket(i);
if (entry != NULL) {
while (entry != NULL) {
tty->print(PTR_FORMAT " ", entry->literal());
entry->literal()->print();
tty->print(" %d", entry->literal()->refcount());
p = entry->next_addr();
entry = (HashtableEntry<Symbol*>*)HashtableEntry<Symbol*>::make_ptr(*p);
}
tty->cr();
}
}
}
#endif // PRODUCT
// --------------------------------------------------------------------------
#ifdef ASSERT
class StableMemoryChecker : public StackObj {
enum { _bufsize = wordSize*4 };
address _region;
jint _size;
u1 _save_buf[_bufsize];
int sample(u1* save_buf) {
if (_size <= _bufsize) {
memcpy(save_buf, _region, _size);
return _size;
} else {
// copy head and tail
memcpy(&save_buf[0], _region, _bufsize/2);
memcpy(&save_buf[_bufsize/2], _region + _size - _bufsize/2, _bufsize/2);
return (_bufsize/2)*2;
}
}
public:
StableMemoryChecker(const void* region, jint size) {
_region = (address) region;
_size = size;
sample(_save_buf);
}
bool verify() {
u1 check_buf[sizeof(_save_buf)];
int check_size = sample(check_buf);
return (0 == memcmp(_save_buf, check_buf, check_size));
}
void set_region(const void* region) { _region = (address) region; }
};
#endif
// --------------------------------------------------------------------------
StringTable* StringTable::_the_table = NULL;
oop StringTable::lookup(int index, jchar* name,
int len, unsigned int hash) {
for (HashtableEntry<oop>* l = bucket(index); l != NULL; l = l->next()) {
if (l->hash() == hash) {
if (java_lang_String::equals(l->literal(), name, len)) {
return l->literal();
}
}
}
return NULL;
}
oop StringTable::basic_add(int index, Handle string_or_null, jchar* name,
int len, unsigned int hashValue, TRAPS) {
debug_only(StableMemoryChecker smc(name, len * sizeof(name[0])));
assert(!Universe::heap()->is_in_reserved(name) || GC_locker::is_active(),
"proposed name of symbol must be stable");
Handle string;
// try to reuse the string if possible
if (!string_or_null.is_null() && (!JavaObjectsInPerm || string_or_null()->is_perm())) {
string = string_or_null;
} else {
string = java_lang_String::create_tenured_from_unicode(name, len, CHECK_NULL);
}
// Allocation must be done before grapping the SymbolTable_lock lock
MutexLocker ml(StringTable_lock, THREAD);
assert(java_lang_String::equals(string(), name, len),
"string must be properly initialized");
// Since look-up was done lock-free, we need to check if another
// thread beat us in the race to insert the symbol.
oop test = lookup(index, name, len, hashValue); // calls lookup(u1*, int)
if (test != NULL) {
// Entry already added
return test;
}
HashtableEntry<oop>* entry = new_entry(hashValue, string());
add_entry(index, entry);
return string();
}
oop StringTable::lookup(Symbol* symbol) {
ResourceMark rm;
int length;
jchar* chars = symbol->as_unicode(length);
unsigned int hashValue = java_lang_String::hash_string(chars, length);
int index = the_table()->hash_to_index(hashValue);
return the_table()->lookup(index, chars, length, hashValue);
}
oop StringTable::intern(Handle string_or_null, jchar* name,
int len, TRAPS) {
unsigned int hashValue = java_lang_String::hash_string(name, len);
int index = the_table()->hash_to_index(hashValue);
oop string = the_table()->lookup(index, name, len, hashValue);
// Found
if (string != NULL) return string;
// Otherwise, add to symbol to table
return the_table()->basic_add(index, string_or_null, name, len,
hashValue, CHECK_NULL);
}
oop StringTable::intern(Symbol* symbol, TRAPS) {
if (symbol == NULL) return NULL;
ResourceMark rm(THREAD);
int length;
jchar* chars = symbol->as_unicode(length);
Handle string;
oop result = intern(string, chars, length, CHECK_NULL);
return result;
}
oop StringTable::intern(oop string, TRAPS)
{
if (string == NULL) return NULL;
ResourceMark rm(THREAD);
int length;
Handle h_string (THREAD, string);
jchar* chars = java_lang_String::as_unicode_string(string, length);
oop result = intern(h_string, chars, length, CHECK_NULL);
return result;
}
oop StringTable::intern(const char* utf8_string, TRAPS) {
if (utf8_string == NULL) return NULL;
ResourceMark rm(THREAD);
int length = UTF8::unicode_length(utf8_string);
jchar* chars = NEW_RESOURCE_ARRAY(jchar, length);
UTF8::convert_to_unicode(utf8_string, chars, length);
Handle string;
oop result = intern(string, chars, length, CHECK_NULL);
return result;
}
void StringTable::unlink(BoolObjectClosure* is_alive) {
// Readers of the table are unlocked, so we should only be removing
// entries at a safepoint.
assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
for (int i = 0; i < the_table()->table_size(); ++i) {
for (HashtableEntry<oop>** p = the_table()->bucket_addr(i); *p != NULL; ) {
HashtableEntry<oop>* entry = *p;
if (entry->is_shared()) {
break;
}
assert(entry->literal() != NULL, "just checking");
if (is_alive->do_object_b(entry->literal())) {
p = entry->next_addr();
} else {
*p = entry->next();
the_table()->free_entry(entry);
}
}
}
}
void StringTable::oops_do(OopClosure* f) {
for (int i = 0; i < the_table()->table_size(); ++i) {
HashtableEntry<oop>** p = the_table()->bucket_addr(i);
HashtableEntry<oop>* entry = the_table()->bucket(i);
while (entry != NULL) {
f->do_oop((oop*)entry->literal_addr());
// Did the closure remove the literal from the table?
if (entry->literal() == NULL) {
assert(!entry->is_shared(), "immutable hashtable entry?");
*p = entry->next();
the_table()->free_entry(entry);
} else {
p = entry->next_addr();
}
entry = (HashtableEntry<oop>*)HashtableEntry<oop>::make_ptr(*p);
}
}
}
void StringTable::verify() {
for (int i = 0; i < the_table()->table_size(); ++i) {
HashtableEntry<oop>* p = the_table()->bucket(i);
for ( ; p != NULL; p = p->next()) {
oop s = p->literal();
guarantee(s != NULL, "interned string is NULL");
guarantee(s->is_perm() || !JavaObjectsInPerm, "interned string not in permspace");
unsigned int h = java_lang_String::hash_string(s);
guarantee(p->hash() == h, "broken hash in string table entry");
guarantee(the_table()->hash_to_index(h) == i,
"wrong index in string table");
}
}
}